Flareless tubes are commonly connected to a tubular fitting body by a nut and ferrule type tube connector assembly wherein a ferrule is placed over the end of a tube, and the ferrule is provided with a sealing face having a configuration adapted to conform to a sealing face defined upon the fitting body to establish a sealing relationship therewith. Often, the ferrule is provided with a deformable portion having an internal edge or serrations adapted to be deformed inwardly into engagement with the associated tube by tightening of a compression nut on the fitting body so as to produce a metal-to-metal sealing relationship with the tube and prevent the tube from axially separating from the fitting such as shown in U.S. Pat. No. 3,109,673 and the assignees U.S. Pat. No. 4,529,231.
Tube connectors of the flareless types are often employed with tubes formed of various materials and hardness, and as the sealing and axial force resistance between the tube and tube connector is dependent upon the engagement of the ferrule with the tube, when connecting tubes of relatively hard materials or nonuniform surfaces, a fluid tight assembly is not always obtained. Even if a fluid tight assembly is initially established, leakage may occur during normal operation due to tubing vibration and deflection if the primary engagement between the ferrule and tube is located adjacent the primary sealing region. Some tube connectors have utilized constructions which have improved the overall performance of the connector, but the results are still less than satisfactory and often the constructions require expensive manufacturing processes.
In U.S. Pat. No. 2,523,135 a tube connector is shown utilizing a double ferrule arrangement wherein one of the ferrules is deformed into a wedge type metal-to-metal sealing engagement with the associated tube. This wedge type of engagement has an advantage over tube connectors employing ferrules which utilize a cutting edge or serrations because a larger contact area is created between the tube and ferrule which produces a more effective seal and provides frictional forces capable of establishing an effective grip on the tube. The outer ferrule has a conical sealing face which establishes a sealing engagement with a conical sealing face defined on the fitting body, and this requires time consuming and expensive machining processes. Also, the end of the tube is not received in a supportive relationship with the ferrule which would provide additional vibration resistance.
In U.S. Pat. No. 2,737,403 a double ferrule arrangement is utilized wherein the end of the tube is received in a sealing engagement with a circumferential undercut defined in one of the ferrules while the other ferrule establishes a sealing engagement with the outer surface of the tube so as to provide a double seal. The undercut portion flares the end of the tube outwardly to create a seal against the ferrule. However, the ferrule which engages the tube outer surface and the nut utilize a perpendicular contact relationship which does not resist vibration loading, and the construction includes abutment shoulders defined on the ferrule and nut which engage to limit nut tightening so if leakage occurs during operation further tightening cannot be accomplished to stop the leakage. Also, the sealing face of the ferrule which engages the fitting body sealing face is of a conical configuration and this requires accurate machining which would not be necessary if the sealing faces were flat.
It is an object of the invention to provide a tube connector of the nut and ferrule type for connecting a flareless tube to a fitting body having a flat sealing face wherein the tube connector is relatively inexpensive to manufacture, simple and efficient to use, dependable in operation, and is capable of being utilized with a wide range of tubing materials of various hardness.
Another object of the invention is to provide a tube connector which utilizes a ferrule and sleeve arrangement wherein the sleeve is provided internally with a circumferential undercut for outwardly flaring the end of the tube and establishing a supporting and locking relationship therewith while the ferrule establishes a wedge type metal-to-metal sealing engagement with the outer surface of the tube so as to provide a double seal.
Yet another object of the invention is to provide a tube connector which utilizes a ferrule and sleeve arrangement operable by a compression nut wherein the sleeve is mounted upon the end of the tube and the ferrule includes front and rear portions, the nut having an internal cam surface adapted to force the ferrule axially forwardly into engagement with the sleeve deforming the front portion into a metal-to-metal sealing engagement with the tube as well as to deform the ferrule into a bowed configuration and its rear portion radially inwardly into the tube to assist in vibration dampening.
An additional object of the invention is to provide a tube connector which utilizes a ferrule, sleeve and compression nut arrangement wherein the construction of the connector does not include means for limiting tightening of the nut and the nut may be sufficiently tightened to establish a double seal between the connector and associated tube to provide a fluid tight assembly.
A further object of the invention is to provide a flareless tube connector employing a sleeve and ferrule wherein a cam surface defined on the sleeve compresses and contracts the ferrule upon the tube, and the sleeve is of such configuration as to permit limited sleeve expansion and radial deformation during ferrule compression to provide a radial biasing pressure on the ferrule.
In the practice of the invention, a fitting body includes a flat radial face having an annular recess defined thereon receiving an elastomeric "O" ring having a greater normal axial dimension than the depth of the recess. The fitting body is externally threaded adjacent its end, and the fitting body may be soldered or threaded upon a tube or other conduit system connection, or otherwise permanently affixed to the conduit system.
A sleeve placed upon the end of a metal tube includes an internal undercut portion adapted to receive and outwardly flange the end of the tube, and the sleeve includes a flat radial surface for engaging the fitting body sealing face and the "O" ring. The sleeve also includes an inner annular conical cam surface adapted to overlie and engage a ferrule and a tapered outer surface to provide clearance for radial expansion. The sleeve includes a cantilevered end which is radially deformed outwardly as the ferrule is compressed which maintains a radial biasing force on the ferrule.
The ferrule is provided with an inner diameter slightly greater than the diameter of the tube, and includes a rear portion and a front portion extending toward the fitting body. A tapered outer surface defined on ferrule is adapted to engage the differently angled sleeve cam surface to deform the front portion of the ferrule into a wedge type metal-to-metal sealing engagement with the tube by a compression nut threaded on the fitting body. The tapered surface of the ferrule is of significantly lesser angle than the sleeve's inner cam surface, causing the ferrule to bow inwardly during assembly. This bowing action creates a compression force within the fitting that absorbs vibration and causes the ferrule to firmly support the tube at a location which is remote from the location of the primary sealing. The nut includes an internal annular conical cam surface which engages a convex abutment surface defined on the ferrule adjacent the rear portion of the ferrule upon rotation of the nut in the tightening direction to force the ferrule axially forwardly and radially inwardly, and engage the ferrule outer surface and sleeve cam surface. This wedge type engagement jams the end of the tube axially forwardly into the sleeve undercut portion flaring the end of the tube outwardly and establishing a locked connection between the tube and sleeve preventing collapse of the tube end. The internal cam surface of the nut also forces the rear portion of the ferrule inwardly into the tube to bow the ferrule which assists in vibration dampening and forces the ferrule rear end into firm contact with the tube for support of the tube at an axial location remote from the ferrule front end where primary sealing is occurring making the connector less susceptible to leakage during operation.
Because the construction utilizes a wedge type sealing engagement with the tube, the tube connector is capable of being employed with a wide range of tubing materials of various hardness.